CROSS REFERENCE TO RELATED APPLICATIONSThis application claims the benefits of U.S. Provisional Application No. 61/382,922, filed on Sep. 15, 2010 and entitled “SMART ANTENNA AND SYSTEM USING THE SAME”, U.S. Provisional Application No. 61/422,660, filed on Dec. 14, 2010 and entitled “SMART ANTENNA SYSTEM”, and U.S. Provisional Application No. 61/425,252, filed on Dec. 21, 2010 and entitled “PORTABLE DEVICE WITH SMART ANTENNA” the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a smart antenna system, and more particularly, to a smart antenna system used in a portable device.
2. Description of the Prior Art
Antenna design is crucial to a portable device with wireless communication function, such as wireless local area network (WLAN) or other mobile communication system. In a conventional wireless communication device, one or a plurality of omni directional antennas are used to receive radio signals from all directions. Antenna diversity technique is also used to determine which one or more omni-directional antennas should be used to receive or transmit signals. However, the efficiency and gain of omni directional antennas are not good enough. Hence, there's a need for an antenna design that provides smarter and better receiving quality.
SUMMARY OF THE INVENTIONIt is therefore an object of the present invention to provide a smart antenna system.
The present invention discloses a smart antenna system for a portable device. The smart antenna system includes a plurality of directional antennas, disposed at a plurality of positions of the portable device, having a plurality of directional radiation patterns corresponding to a plurality of areas; wherein all of the plurality of directional radiation patterns substantially form an omni directional radiation pattern.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a schematic diagram of a smart antenna system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of the smart antenna system shown inFIG. 1 according to an alteration of the present invention.
FIG. 3A is a schematic diagram of a smart antenna system utilized in a laptop according to an embodiment of the present invention.
FIG. 3B is a schematic diagram of efficiencies of a conventional omni directional antenna system with antenna diversity and the smart antenna system shown inFIG. 3A according to an embodiment of the present invention.
FIG. 3C is a schematic diagram of ideal gain improvement of the smart antenna system shown inFIG. 3B according to an embodiment of the present invention.
FIG. 4 is a switching process according to an embodiment of the present invention.
DETAILED DESCRIPTIONPlease refer toFIG. 1, which is a schematic diagram of asmart antenna system10 according to an embodiment of the present invention. Thesmart antenna system10 is utilized in aportable device12. Thesmart antenna system10 includes directional antennas ANT1-ANT4. The directional antennas ANT1-ANT4are disposed at4 positions of theportable device12, e.g. a left side, a right side a bottom side and a top side around theportable device12, and have directional radiation patterns DRP1-DRP4corresponding to areas A1-A4. All of the directional radiation patterns DRP1-DRP4substantially form an omni directional radiation pattern. Noticeably, an amount of directional antennas included in thesmart antenna system10 is not limited to any specific number, as long as radiation patterns thereof can substantially form an omni directional radiation pattern to receive and transmit signals from all directions.
Noticeably, compared with an omni directional antenna, an ordinary directional antenna has many advantages in a corresponding directional radiation pattern, such as high gain for desired signal, long transmission distance, better received signal strength indication (RSSI), low side lobe for interference, low noise floor, and low power consumption under the same Equivalent isotropically radiated power (EIRP) requirement, etc. Therefore, in such a configuration, the omni directional radiation pattern substantially formed by the directional radiation patterns DRP1-DRP4has better efficiency than an omni directional radiation pattern formed by one or a plurality of omni directional antennas. As a result, thesmart antenna system10 can have better gain and efficiency.
In a preferable case, no directional antenna of the directional antennas ANT1-ANT4has a directional radiation pattern directing toward a user of theportable device12, and signals from a direction of the user can be received by the directional antennas ANT1-ANT4through multi-path, e.g. reflection by objects, such that the user may not be harmed by radiation. For example, the directional antennas ANT1-ANT4shown inFIG. 1 can be disposed on sides around a display of theportable device12, and another directional antenna ANT5(not shown) can further be disposed on a back side of the display of theportable device12, such that the user can operate theportable device12 without being harmed by radiation.
On the other hand, please refer toFIG. 2, which is a schematic diagram of thesmart antenna system10 shown inFIG. 1 according to an alteration of the present invention. In order to enhance efficiency in wireless transmission, thesmart antenna system10 can further include awireless module202, for switching to utilize one of the directional antennas ANT1-ANT4to receive and transmit signals at a time. Therefore, thesmart antenna system10 can preferably only utilize a directional antenna with a best efficiency among the directional antennas ANT1-ANT4to receive and transmit signals and thus save power, wherein the directional antenna with the best efficiency is a directional antenna having a directional radiation pattern corresponding to an area where a signal source is located.
In detail, thewireless module202 includes aswitch204 and awireless chip206. Theswitch204 can be a single pole four throw (SPOT) switch or a SPnT in other cases. Thewireless chip206 is coupled to theswitch204, and controls theswitch204 to connect with one of the directional antennas ANT1-ANT4through General Purpose Input/Output (GPIO) interfaces or other interfaces. As a result, thewireless chip206 can preferably control theswitch204 to connect to the directional antenna with the best efficiency among the directional antennas ANT1-ANT4according to a location of a signal source, so as to utilize the directional antenna with the best efficiency to receive and transmit signals at a time.
Take a laptop for example, please refer toFIG. 3A, which is a schematic diagram of asmart antenna system30 utilized in alaptop32 according to an embodiment of the present invention. As shown inFIG. 3A, directional antennas ANT6-ANT8are disposed on a left side, a right side and a top side of adisplay34 of thelaptop32, respectively, and another directional antenna ANT9is disposed on a back side of thedisplay34 of theportable device32. The directional antenna ANT9can be a parallel patch array antenna since a space between a frame and the back side of thedisplay34 is very thin, and may have the highest efficiency, such as a maximum antenna gain of 7 dB, while the directional antennas ANT6-ANT8can be series dipole array antennas since spaces between a frame and the left side, the right side and the top side of thedisplay34 are very narrow, and may have an antenna gain of 5 dB.
Noticeably, no directional antenna has a directional radiation pattern directing toward a user of thelaptop32, and thus the user should not be harmed by radiation. In such a configuration, when thesmart antenna system30 determines the directional antenna ANT9with the best efficiency, i.e. a signal source is located in an area corresponding to the directional antenna ANT9, thesmart antenna system30 switches to thesmart antenna system30 to receive and transmit signals.
As a result, please refer toFIG. 3B, which is a schematic diagram of efficiencies of a conventional omni directional antenna system with antenna diversity and thesmart antenna system30 shown inFIG. 3A according to an embodiment of the present invention.FIG. 3B is obtained by setting the omni directional antenna system and thesmart antenna system30 on a turn table and transmitting signals to the omni directional antenna system and thesmart antenna system30 with 30 dB attenuation by a fixed signal source to measure throughputs while the omni directional antenna system and thesmart antenna system30 are turned by 360°, respectively. Noticeably,FIG. 3B is an experimental result, and the experimental result is distorted since thesmart antenna system30 in experiments has a narrower space on the right side)(90° than that on the left side)(270°. Ideally, throughput on the left side should be identical to that on the right side.
Please refer toFIG. 3C, which is a schematic diagram of ideal gain improvement of thesmart antenna system30 shown inFIG. 3B according to an embodiment of the present invention. InFIG. 3C, the directional antenna ANT9has highest antenna gain and thus highest gain improvement. Noticeably, though no directional antenna has a directional radiation pattern directing toward the user, signal gain of a direction corresponding to the user can still be improved due to multi-path reception. As shown inFIG. 3B andFIG. 3C, thesmart antenna system30 can have better receiving and transmitting efficiency than the omni directional antenna system.
Noticeably, the spirit of the present invention is to arrange a plurality of directional antennas around a portable device, so as to substantially form an omni directional radiation pattern. Those skilled in the art shout make modifications or alterations accordingly. For example, theportable device12 is preferably a laptop, but can be a tablet computer, a mobile phone etc.
Furthermore, a movement of theportable device12 may be a factor to trigger a switching mechanism of thewireless chip206 to determine which directional antenna has a best efficiency among the directional antennas ANT1-ANT4and control theswitch204 correspondingly since corresponding areas of the directional antennas ANT1-ANT4are changed.
In detail, since the directional antennas ANT1-ANT4are directional, the change of RSSI at each antenna may be used to simulate or estimate the movement of theportable device12. For example, a steady RSSI may imply theportable device12 is at a steady state, which does not need to switch the currently used directional antenna. On the contrary, thewireless chip206 starts determining which directional antenna has the best efficiency among the directional antennas ANT1-ANT4if an RSSI of a currently connected antenna varies beyond a threshold X dBm, so as to control theswitch204 correspondingly.
Specifically, thewireless chip206 controls theswitch204 to connect with each of the directional antennas ANT1-ANT4for a predefined time t to collect a statistical information of the each of the directional antennas ANT1-ANT4, and determines which directional antenna has the best efficiency according to all statistical information of the directional antennas ANT1-ANT4. The statistical information may include at least one of an average RSSI, a packet error rate (PER), and a total successful packet number during a period. Besides, since the directional antenna has the best efficiency may not perform best in all of the average RSSI, the PER, and the total successful packet number due to non-ideal factors, thewireless chip206 determines which directional antenna has the best efficiency according to a weighting W of the average RSSI, the PER, and the total successful packet number during a period. Noticeably, the threshold X, the predefined time t and the weighting W have to be adjusted due to practical requirement. As a result, thewireless chip206 can control theswitch204 to connect to the directional antenna with the best efficiency when theportable device12 moves.
Moreover, thewireless chip206 can determine which directional antenna has a best efficiency among the directional antennas ANT1-ANT4periodically, every predetermined time T, since a currently used directional antenna may not be a directional antenna actually having the best efficiency, e.g. there may be obstruction between a signal source and the directional antenna actually having the best efficiency during determination. As a result, thewireless chip206 can determine which directional antenna has a best efficiency among the directional antennas ANT1-ANT4periodically, to ensure the currently used directional antenna actually has the best efficiency.
Operations of thewireless module202 can be summarized into a switching process40 as shown inFIG. 4. The switching process40 includes the following steps:
Step400: Start.
Step402: Determine whether a currently connected antenna is connected for a predetermined time T. If yes, go to step406; otherwise, go to step404.
Step404: Determine whether an RSSI of the currently connected antenna varies beyond a threshold X dBm. If yes, go to step406; otherwise, go to step410.
Step406: Connect with each of the directional antennas ANT1-ANT4for a predefined time t to collect a statistical information of the each of the directional antennas ANT1-ANT4. Determine if all statistical information of the directional antennas ANT1-ANT4is collected. If yes, go to step408; otherwise, go to step406.
Step408: Determine which directional antenna has the best efficiency according to all statistical information of the directional antennas ANT1-ANT4, and switch to connect to the directional antenna with the best efficiency.
Step410: End.
Detailed operations of the switching process40 can be derived by referring to the above description.
In the prior art, efficiency and gain of omni directional antennas are not good enough. In comparison, the present invention arranges a plurality of directional antennas around a portable device, so as to substantially form an omni directional radiation pattern, and thus have better gain and efficiency. Moreover, the present invention can determine which directional antenna has the best efficiency when the portable device moves or periodically, so as to ensure a currently used directional antenna has the best efficiency.
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.